Silvanus phillips thompson



(No Model.)

S. P. THOMPSON.

ELECTRIC CABLE.

No. 571,706. Patented Nov. 17,1896.

VUUUUU UNITED STATES PATENT OFFICE.

SILVANUS PHILLIPS THOMPSON, OF LONDON, ENGLAND.

ELECTRIC CABLE.

SPECIFICATION forming part of Letters Patent No. 571,706, ated November17', 1896.

Application filed July 20, 1892. Serial No. 440,672. (No model.)Patented in England December 21, 1891, No. 22,304, and

July4, 1893, No. 13,064; in France June 20, 1892, No. 222,460, andDecember 13, 1803,1I0. 234,763; in Germany Octobe! 23, 1892,10). 86,013;in India April 25, 1893, No. 320, and August 1139 1110418; in SpainSeptember Noil8,896, and April 10,1894,1 T0.15,306; in Brazil February'7,1894,N0.1,686; in Ceylon August 22, 1894, Not 443,

and in Straits Settlements Decem er 14, 1895.

To all whom it may concern:

Be it known that I, SILVANUS PHILLIPS THOMPSON, doctor of science, asubject of the Queen of Great Britain, residing at Moi-land, OhislettRoad, est IIampstead, London, in the county of Middlesex, England, haveinvented certain new and useful Improvements in Electric Cables, (forwhich I have obtained patents in Great Britain, No. 22,304, datedDecember 21,1891, and No. 13,064, dated July 4, 1803; in France, No.222,460, dated June 20, 1802, and No. 234,763, dated December 13, 1803;in Germany, No. 86,013, dated October 23, 1802; in Spain, No. 13,806,dated Septem her 4, 1803, and No. 15,306, dated April 10, 1804; inIndia, No. 320, dated April 25, 1803, and No. 18, dated August 17, 1804;in Brazil, No. 1,686, dated February 7,1804; in Ceylon, No. 443, datedAugust 22, 1804, and in Straits Settlements, dated December 14, 1805,)of which the following is a specification.

Thisinvention is applied for under the Con vention for the Protection ofIndustrial Property, my English application for the same invention, No.22,304, being dated the 21st day of December, 1801.

My invention pertains to electric signaling for telegraphic, telephonic,or other purposes through long lines or cables, and has for its chiefobjects to extend the distance to which such signaling can be carried onand to increase the rapidity and facility of signaling.

By signaling I mean the communicating of any sort of signals, whetherspoken words, as in telephonic signaling, or humming sounds, as inharmonic telegraphs, or rapidlyreversed impulses, like those used inrapid automatic telegraphy, or dot-and-dash signals due to interruptionsor reversals of cur rent, or deflections of a needle to right and left,or motions of a siphon-recorder or of the tongue of a relay.

As lines and cables are now constructed there is a practical limit tothe distance to which signaling is possible with existing instruments.My invention will increase this distance. There .is also for a line orcable of given length, as at present constructed, a

E limit to the rapidity at which signals can be transmitted byinstruments of a given type. My invention will increase this rapidity ofsignaling. There is, moreover, for a line or cable of given length, asat present constructed, a limit to the kind of instrument that can beused to signal, high-speed instruments, harmonic telegraphs, andtelephones not being capable of being used on long cables or on verylong lines. My invention will ex- ,tend the facility of signaling byrendering lines and cables available for instruments for which they arenot now available. It will also increase the facility of signalingthrough cables by enabling signaling to be carried on without suchexpensive arrangements for securing balance, known as artificial cables,as at present used at the shore ends.

It is known that the presence in cables and lines of electrostaticcapacity limits the rate of signaling and the distance of signaling, aswell as limits the kinds of signals that can be sent to a givendistance. For example, the capacity of an Atlantic cable, which is aboutone-third microfarad per nautical mile, re tards telegraphic signals somuch that only a few words per minute can be transmitted. The distanceto which rapid automatic signals can be sent through cables of this typeis but a few score miles. Through very long cables of existing typestelephones, harmonic telegraphs, and rapid automatic instruments cannotbe used at all.

It is known that the cause of the limitations mentioned above, as foundwith cables and long lines of existing type, is the presence ofelectrostatic capacity. Such electrostatic capacity is in general notlocated at any one point,but is distributed more or less uniformly alongthe line or circuit, Now by my invention I counterbalance the effects ofthis distributed capacity by applying distributedelectromagneticinduction. Electromagnetic induction is the action whichthe rise or fall of the current in any part of the circuit pro duces onthe same or any other part of the circuit by virtue of the fact thatevery Varyin g current produces around it a varying magnetie field.\Vhen the current is varying in a wire or coil, the varying magneticfield around it induces electromotive forces in neighboring conductorsor coils or in other convolutions of the same wire or coil. lly properdispositions, as hereinafter further described, such electromagneticinduction, if suitably distributed along the cable or line, may beutilized to diminish, or even to nontralize for all effective purposes,the retarding and limiting effects of electrostatic capacity. Fnder themost favorable dispositions the whole of the electrostatic capacity iscounterbalanced, and then the retarding and limiting effects will beneutralized. here the conditions or arrangements are less favorable, apart only of the electrostatic capacity will be counterbalanced, and insuch cases the retarding and limiting effects, though not ontirelyneutralized, will be diminished. hen the arrangements are such as tothus balance the distributed capacity and neutralize the retardingeffects, then the system will conduct, like any ordinary plainconductor, the current shuntedoff through the compensators following theordinary laws of current flow.

The present invention consists in introducing into the electric circuitat intervals what I may term compensators possessing electromagnetic induction su fficient, more orless, completely to balance the distributedcapacity. bearing in mind the average frequency ofthe electric impulses,whether telegraphic, telephonic, or other, which are to be tranr mitted.The electrostatic capacity distributed along the cable or line is thusbalanced, as it were, in sections, each organ so introduced into theline or cable exerting a nontralizing effect on the capacity of thecable in the adjacent parts. Thus, for example, if a self-inductioncoil, inserted as hereinafter described, is of sufficient size and powerto approximately neutralize the effects of electrostatic capacity of anycable for a distance of five miles on either side from the point whereit is inserted it will be expedient to treat that cable in sections eachof ten miles length, similar self-induction coils being inserted everyten miles along the cable. It is an important point that these coilsshould be all alike for any given sample of cable and at approximatelyequal distances apart. Self-induction coils for use as compensatorsshould also have not only a high-time constant, but a high resistancerelatively to that of the section of cable which they are to compensate.In cases where it is important to avoid a material weakening of thetransmitted currents from flow through the compensators it is preferablethat the resistance of the compensators should be greater than that ofthe entire cable. These coils should have each such dimensions and bemade with such a number of turns of wire of such a gage (wound around awell-laminated iron core of such shape and length) that the timeconstant (or interval of time that is needful :for i the current in thesaid coil to rise to 0.0% of its final value) shall be not less than,and shall be preferably greater than, one one-hundredth of a second,while the resistance of the said coil shall be much greater than that ofthe ten-mile or twenty-mile section of the cable, and shall, indeed, inthe cases just previously mentioned, be with advantage as great as orgreater than the resistance of the entire length of the conductor. Inelectric cables they must be further arranged so as not to form unwieldyenlargements of the cable. nary iron cores will not do. Iron cores,whenthey are employed, must be made of a relatively small amount of verywell laminated iron.

Referring to the drawings, Figure 1 shows the simplest form ofcompensator diagrammatically. Fig. 2 is a single line with a compensatorconnecting it with return; Fig. 23, two wires with separate eompcnsatorsconnecting them with return Fig. -.l-, an inner and outerconductor, theouter only provided with compensators; Fig. 5, three lines joined bycompensators; Fig. 6, where two lines are joined by compensators and athird is connected to the centers of these compensators by coils of halfthe length of the other compensa-tors. In this way a star ofcompensators could be formed, uniting several wires with coils of equallength to'one point or wire. Fig. 7 shows two wires in the same cable atintervals coiled in opposite directions around each other or around acommon core.

In Fig. 1, A is the conductor; l3, the sheath; 0, a shunt from theconductor to the sheath coiled around the conductor, which at this pointis preferably composed of numerous line wires insulated by rust orotherwise from each other, so as to form a laminated core. The coil isof course, as well as the core, covered with insulating material. Thechoking or self-inducting action of this coil, if of sufficient numberof turns near together, causes sufficient resistance (which, as beforestated, must be greater than the entire circuit) through the conductorto prevent all but an insignificant quantity of the working charge toshort circuit.

It is obvious that instead of B in the drawing being the sheath it wouldact just as well if it were the return-wire. In this latter case itwould be desirable for each alternate coil to be around the return, theremainder being around the lead. Such an arrangement is shown in Fig. 7.In said Fig. 7, however, no coils are shown, the lead and returnconductors which are alternatelycoiled one about the other acting bymutual induction.

In Fig. 2, A is the lead-conductor, B the re turn, and D aself-induction coil connecting A and B.

In Figs. 3 and i, A is the main conductor, 13 the return or the sheathactingasarcturn, and A is an outer conductor surrounding the inner oneA.

Ordinary eleetromagnets with ordi- In Figs. 5 and 6, A A A areconductors, and D self-induction coils. The self -induction coils D haveeach a thin core of fine wires in a parallel laminated bundle.

In Fig. 7 is seen an arrangement in which the conductor and return-wiresare coiled about each other alternately.

The various arrangements shown will be used according to circumstances,and it will also be apparent to the skilled electrician that in practiceother modifications may suggest themselves in view of the disclosedinvention and without departure therefrom.

I declare that what I claim is 1. In an electric cable havingcontinuouslyinsulated metallic conductors from end to end, thecombination with the said conductors of a series of compensators ordevices possessing both resistance and self-induction, systematicallydistributed at intervals along the entire length of the cable, soproportioned and arranged that their electromagnetic induction shallcounterbalance from point to point the effect of the distributedelectrostatic capacity of the gutta-percha surrounding the saidconductors.

2. A cable divided into sections, in each of which is an electromagneticinduction device connecting the conductors, and forming a structural andintegral part within the outer sheathing of the cable, each saidelectromagnetic induction device being so proportioned as tocounterbalance the electrostatic capacity of the particular section towhich it is applied, whereby the capacity of the section iscounterbalanced.

3. The combination of two or more conductors in a cable withshort-circuiting ind uctioncoils placed between the conductors havingeach a resistance at least as great as that of the portion of theconductor between each such coil and the next, whereby the statioalcharges otherwise accumulating along its entire length, are drawn off atintervals along the length.

i. I11 a cable, the combination with the conductors thereof, one ofwhich is formed at intervals as a laminated core, of a shunt extendingfrom the other conductor and coiled around a laminated core in a coil ofgreater resistance than that of the entire circuit.

5. A cable having its conductors united at periodic intervals by shuntswhich are coiled around cores, and which have each a greater resistancethan the combined resistance of the conductors between any suchshunt-coil and the next such shunt-coil.

('3. In an electric cable having continuouslyinsulated conductorsrunning therethrough side by side, the combination within said cable ofa conductor and a return-wire with ind notion-coils having their axesapproximately parallel with the axes of the conductors.

7. The combination of two conductors which would if uncompensatedexercise electrostatic retarding effects on one another by mutualcapacity, with a self-induction coil or coils connectin them, of greaterresistance than their circuit or circuits, such coil or coils possessinga high time constant and having a small and highly laminated core.

8. In an electric cable having two continuous insulated conductors, thecombination of the said conductors with a self-induction coil or devicewhich is connected across as an oblique bridge from one conductor to theother, one end of the said device or bridge being joined to one of theconductors at a point farther along the cable than that at which theother end of the said device or bridge is connected to the otherconductor.

0. A cable comprising two or more insulated conductors runningtherethrough side by side and provided at intervals with compensatingdevices for diminishing the electrostatic ca pacity.

In testimony whereof I have signed my name to this specification in thepresence of two subscribing witnesses.

SIL'HNUS PHILLIPS THOMPSON.

lVitnesses:

WALTER P. RERTEN, T. F. BARNES.

